The good news about e-reader apps for smartphones is that you have a selection to pick from. Most are available in multiple phone formats and allow you to adjust the page background and font size, and to sync your books with the different devices you own [source: Biersdorfer]. Here are two of the most popular apps:

Amazon Kindle for phones: Kindle, the most popular e-reader device brand, also offers an e-reader phone app that works on the widest range of operating systems -- iPhone, Android, BlackBerry and Windows Phone 7. All of them offer Amazon's ingenious Whispersync feature, which will automatically save and sync your bookmarks, notes, highlights and the last page read across multiple devices. That way, if you start out reading a book on your laptop or Kindle at home, you can pick up where you left off on your phone later. The Kindle app gives you access to 1 million Kindle-format books available for download on the Amazon Web site, including thousands of free titles -- mostly public domain classics like Jane Austen's "Pride and Prejudice." You can also download books available on loan from your local library [source: Amazon.com].

Barnes & Noble Nook app: Versions are available for both iPhone and Android phones. The app gives you access to 2.5 million books, magazines and newspapers, and allows you to sample a selection of new releases, bestsellers, classic books and magazines for free for 14 days. Like the Kindle app, if you use the Nook app on both a phone and a tablet or laptop, it will automatically sync your bookmarks and your last page to all your devices. The Android version has an additional feature -- LendMe, which allows you to share your purchases with a friend for a couple of weeks [source: Barnes & Noble].

Those are a couple of good e-reader app options, but which is the best for you?